Synthesis of helically twisted [1 + 1]macrocycles assisted by amidinium–carboxylate salt bridges and control of their chiroptical properties

Abstract

A series of optically active, helically twisted [1 + 1]macrocycles connected via o-, m-, and p-linkages (o-2, m-2, and p-2) was prepared from the corresponding linear duplexes stabilized by complementary amidinium–carboxylate salt bridges bearing two arms with terminal vinyl groups at both ends through the ring-closing metathesis reaction in the good yields of 67, 92, and 96%, respectively. The chiroptical properties of the macrocycles were dependent on the linker geometries and could be controlled by acid–base interactions and zinc coordination, the changes in which were detected by their CD and absorption spectral changes and fluorescence colors.